1. Field of the Invention
This invention relates to a joint construction for cable piping.
2. Description of the Related Art
Conventionally, as a joint construction for cable piping used to obtain an expansion length for earthquakes and a temperature change in pipings buried in the ground to include cables for communication and transmission, an end side of each of two second cylindrical bodies is inserted to both opening portions of a first cylindrical body, respectively, as to relatively move in an axis direction within a certain range, each of third cylindrical bodies being fitted onto another end of each of the second cylindrical bodies through a spherical joint respectively as to relatively oscillate, and both ends of this joint are flanged onto pipings (Japanese provisional publication No. 10-169865, or example).
However, for the cable piping buried in the ground, to secure the communication network uncut even in a large earthquake, a joint construction, which can obtain a larger expansion length than that of a conventional expansion joint, is required. Further, the conventional joint construction has a large number of parts including at least five cylindrical bodies, spherical working for the spherical joint is required, and assembly of the joint requires fastening with bolts and nuts because the piping to be connected to each of the both ends of the joint has a flange.
The inventors of the present invention have proposed a construction described in Japanese patent application number 10-317155 to secure sufficient expansion length as a joint construction for piping (Japanese Patent No. 3048559).
However, the joint construction proposed in Japanese patent application number 10-317155 has the following problems. That is to say, firstly, the production process is complicated because the number of parts is large and welding is needed for assembly. Secondly, when press-fitting (caulking) is applied instead of the welding, configurations of other parts not relating to the connection is deformed by working force (causing deformation). Third, the construction tends to generate problems in sealability as a joint having long expansion length. Fourth, the piping tends to be unexpectedly drawn out for insufficient rigidity of a hitching blade of a stop ring. Fifth, the piping is hard to insert in some cases. These remaining problems have been revealed.
It is therefore an object of the present invention to provide a joint construction for cable piping in which large expansion length in an axis direction of the piping can be secured with a simple construction having a small number of parts, and production is made easy.